Vehicle Transmission Gradient Control During Braking
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Solution Overview
Problem
Existing automatic transmission systems for vehicles inaccurately determine road gradient when braking, leading to inconsistent shift points and potential driver misinterpretation of malfunctions, as the braking torque interferes with engine torque-based gradient determination algorithms.
Innovation Solution
A method that continuously determines tractive and braking efforts while accounting for real-time changes in vehicle speed, summing these efforts to calculate net effort, which is then compared to base data to accurately assess the road gradient and select appropriate transmission shift points, even during braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gradient determination is performed using engine torque and acceleration, then gradient detection is possible, but the determination becomes inaccurate when brakes are applied due to braking torque interference
Solution Approach 1:
The system dynamically adjusts the gradient determination method based on braking status. When braking is detected, the system switches from using engine torque alone to using the sum of engine torque and braking torque, thereby adapting to different operational conditions and maintaining accuracy across all scenarios
Solution Approach 2:
The system changes the parameter used for gradient determination based on braking status. The gradient determination parameter is switched from engine torque (Teng) to the sum of engine torque and braking torque (Teng + Tbrk) when braking is detected, ensuring accurate gradient measurement regardless of braking intervention
2Reliability
If gradient determination is disabled during braking, then accuracy is maintained, but the system cannot provide shift point control during braking operations
Solution Approach 1:
The system converts the harmful effect of braking torque interference into a beneficial solution by incorporating braking torque into the gradient determination calculation. This allows the system to maintain reliable and consistent shift point control even during braking operations, transforming a previously problematic condition into a manageable scenario
3Use of energy by moving object
If multiple shift maps are provided for different gradients, then fuel efficiency is improved, but the system complexity increases
Solution Approach 1:
The system prepares multiple shift maps in advance for different gradient conditions and selects the appropriate map based on real-time gradient determination. This preliminary preparation allows the system to quickly switch between optimized shift maps for different gradients, maintaining fuel efficiency without requiring complex real-time calculations
Solution Approach 2:
The gradient determination system serves multiple functions: it determines road gradient for shift map selection, detects braking status, and selects appropriate shift maps for different operating conditions. This multi-functionality reduces the need for separate systems, thereby limiting the increase in overall system complexity while still achieving improved fuel efficiency
Data Source
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AI summary
A method and system of determining the instant gradient of a road, taking into account positive and negative drive torque, may be used to select one of a plurality of shift maps for a vehicle automatic transmission. The invention takes into account vehicle retardation due to braking, and permits consistent adoption of a shift map appropriate to the instant gradient.